To reduce friction and enable a drawer to withstand a heavy load, drawer slides for furniture in file cabinets and other furniture employ bearings to reduce wear, Professional furniture for medical, industrial, and engineering applications often requires thin drawers and thin drawer slides. Such applications also require a heavy-duty slide. Four sets of ball bearings are usually required to bear a typical load when full extension is required. However, the use of four separate sets of ball bearings poses obstacles to miniaturization of the slide. Furniture designers desire the cross-section profile of the slide to be thin in the horizontal direction, thereby enabling a drawer to be as wide as possible compared to the opening in which it slides. Moreover, designers want slides which are shallow in the vertical direction to keep the slide unobtrusive, and enable use with short drawers.
In most drawer slides of the prior art, the four separate ball bearing assemblies are aligned in pairs on two spaced-apart vertical axes. To make a drawer slide thin in the horizontal direction, designers have focused on making the relative vertical separation of one pair of bearings narrower than the other. This enables the vertical axes of the bearing pairs to become nearly collinear, resulting in a thin slide.
For example, U.S. Pat. No. 5,022,768 (Baxter) discloses, in FIG. 1, a prior art slide mechanism in which the ball bearing pairs are on nearly collinear vertical axes. FIGS. 3, 4, and 7 of U.S. Pat. No. 4,469,384 (Fler et al.) discloses a similar collinear axis slide. However, the cross-section profile of the resulting slide is not symmetrical, requiring the separate fabrication of a fixed cabinet member and a moving drawer member, each having a different cross-section. This increases manufacturing costs and increases the height profile of the slide.
Thus, designers of drawer slides desire to provide a slide which is horizontally thin and vertically short to enable unobtrusive installation in a variety of furniture mounting arrangements. Designers of drawer slides also desire to provide a slide in which the central slide member is structurally stable.
Another goal of slide design is smooth control of extension of the slide. U.S. Pat. No. 4,662,761 discloses a multi-part slide with a roller 18. This slide requires four outside channel members and separate plates 57, 58 to join the channels together. The bearings are arranged on a vertical collinear axis. The roller 18 has a horizontal axis of rotation and provides sequential motion rather than smooth progressive movement.
U.S. Pat. No. 3,966,273 shows a slide with progressive movement control of a ball retainer using bands of material which impose friction. U.S. Pat. No. 3,901,564 shows a slide with a progression roller 38 having a horizontal axis of rotation. The roller imposes friction on the outer channel members of the slide.
U.S. Pat. No. 3,857,618 shows control of a ball retainer using a rack and pinion arrangement best seen in FIG. 11. The pinion gear has a horizontal axis of rotation but requires clearance space at the bottom of the slide channel members, thereby increasing the overall height of the slide. Punched holes are required in the slide.
U.S. Pat. No. 3,679,275 shows a drawer slide with four outer channel members and a roller 66 mounted on a vertical shaft 68. The roller has a knurled outer surface which imposes friction on the inside faces of outer plates 16, 36 which hold the four channel members together. This requires special preparation of the slide member surfaces, which leads to higher manufacturing costs and greater complexity of design. Also, the '275 patent requires two separate sets of sliding components.
Thus, the prior art fails to provide a drawer slide which is horizontally thin and vertically shallow or short, and also incorporates a progression roller system. The prior art also fails to provide a slide with a progression roller which can facilitate closure of the slide, act as a detent, and also release pressure on the roller when the slide is closed. A particular disadvantage of prior art slides with progression rollers is that when closed, the roller is in constant compression within the slide. This results in permanent flattening or deformation of the roller over time. This causes undesirable bumpy movement of the slide.